In recent years, there has been an increasing demand for improvement against fogging and fouling that occur on substrate surfaces such as plastic surface and glass surface.
As a method for solving this problem of fogging, an antifogging coating material prepared by adding a reactive surfactant to an acrylic oligomer has been proposed and a cured film obtained from this antifogging coating material is described to have improved hydrophilicity and water absorption properties (Non-Patent Document 1). In addition, for example, as a method for solving the problem of fouling, antifouling materials having self-cleaning properties (antifouling properties) that improve the surface hydrophilicity and allow dirt (hydrophobic substance in ambient air, etc.) adhered to an external wall or the like to come off and be efficiently removed with rainfall, sprinkled water or the like have been attracting attention (Non-patent Documents 2 and 3).
As a means of completely overcoming these problems of “fogging” and “fouling”, the present inventors proposed a monolayer film in which anionic hydrophilic groups are biased (concentrated) to the surface (Patent Document 1). The hydrophilic film obtained by the invention is transparent and extremely highly hydrophilic and has excellent antifogging, antifouling, antistatic and quick-drying (high drying rate of adhered water) properties as well as excellent chemical resistance. Besides, this hydrophilic film is hard and also has excellent scratch resistance. However, investigations by the present inventors revealed that the hydrophilic film is not satisfactory in terms of abrasion resistance and weather resistance.
Generally, as a method for attaining excellent weather resistance and improving the abrasion resistance of a surface, a method of coating an inorganic compound is known. Representative examples of the use of such a method include a case where a silica compound prepared by sol-gel reaction is used as a hard coat of a spectacle lens (Non-patent Document 4).
A silica coating has a dense structure; therefore, it is extremely hard and its abrasion resistance reaches a level that is comparable to that of glass. However, at the same time, there are also problems, for example, that it is readily cracked and cannot be stained and that it readily allows dirt to adhere and to be fixed thereon. As a method of solving these problems, a variety of proposals have been made. For example, as a method of imparting staining property and toughness, a method of incorporating a melamine-polyhydric alcohol condensate and an epoxy group-containing silane compound into silica (Patent Document 2), a method of incorporating an epoxy compound and an aluminum complex into silica (Patent Document 3) and a method of incorporating a hydroxy group-containing acrylic polymer into silica (Patent Document 4) have been proposed.
As a method of imparting antifogging property by hydrophilization, a method of incorporating a styrene-based sulfonic acid polymer into silica has been proposed (Patent Document 5).